The present invention relates to a suction device for a hand-held power drill, especially for a hand-held power tool using a drilling bit, and to a control method for this purpose.
The amount of drilling dust obtained varies depending on the area of application. A suction device is frequently not required. A modular suction device is therefore desired, which a user can attach and release once again from a hand-held power tool with a few manipulations and without any tool. Adaptations of the hand-held power tool for a joint use with the suction device should be kept to a minimum.
An inventive suction device for a hand-held power drill in accordance with the present invention has a housing and a locking device for fastening the housing to a housing of a hand-held power drill. A user can attach and remove the suction device without tools. The suction device furthermore has a fan motor and a controller for the fan motor. The controller contains a sensor for detecting the operating state of an electric motor of the hand-held power tool. The controller is set up to activate the fan motor when the electric motor is in a rotating state of operation. The hand-held power tool does not contain any additional circuits or arrangements, which ensure that the suction device is switched on. Likewise, a switch element, which has to be activated by the user, is not required at the suction device.
One embodiment provides that the sensor detects a magnetic field generated by the electric motor and activates the control mechanism of the fan motor when the strength of the magnetic field exceeds a threshold value. The magnetic field proves to be a robust feature, which is not distorted by interfering signals even under the rough operating conditions of drilling, especially those encountered when a hand-held power drill is used with a drill bit. The sensor is able to detect a static magnetic field generated by the electric motor. The sensor is able to detect an alternating magnetic field produced by the electric motor and to supply the signal of the sensor to a high pass filter. The latter proves to be independent of the electric motor used in the hand-held power tool.
A switch may be disposed between the power supply of the suction device and the control system. The sensor contains a transducer coil, which is coupled with a switch in such a manner, that a current, induced in the transducer coil by the electric motor, switches the switch. This is of advantage especially when the suction device is supplied by a battery package. A loss of power due to a control system actively checking the sensor is avoided.
In accordance with one embodiment, the control system contains a timer, by means of which the switching off of the fan motor is delayed when the operating state of the electric motor is changed to a stationary state. The fan motor is switched on preferably immediately when there is a change to the rotating state of operation.
A control method for a suction device, which is designed for a hand-held power drill, employs the following steps in an embodiment: the operating state of an electric motor of the hand-held power tool is determined by a sensor in the suction device. A fan motor of the suction device is activated when the sensor detects a change in the operating state of the electric motor to a rotating operating state. The fan motor of the suction device is deactivated when the sensor detects a change in the operating state of the electric motor to a stationary operating state. The fan motor is activated preferably without delay after the change into the rotating state of operation; the deactivation of the fan motor, on the other hand, may be delayed when the operating state is changed to a stationary one.
The following description explains the invention by means of embodiments, given by way of example, and by means of Figures.